Improved bag for the cultivation of mushroom spawn

Abstract: An improved bag 20 for the cultivation of mushroom spawn has front and back walls 22, 24 having a plurality of openings 26 disposed therethrough, a top 28 and a bottom 30, and left and right sides 32, 34. A plurality of gas permeable sealing strips 36, 38 are sealed to the walls 22, 24 and cover each of the openings 26. The openings 26 are arrayed in a pair of parallel rows 42, 44 proximate respectively the top 28 and the bottom 30 of the bag 20 so as to provide more uniform breathability of the mushroom spawn through the gas permeable sealing strips 36, 38, the openings 26 and the gas permeable sealing strips 36, 38 being constructed and arranged so as to reduce dry spots in the mushroom spawn and improve spawn yield.

Description: The present invention relates generally to plastic bags and more particularly to a novel air permeable bag suitable for use in the cultivation of mushroom spawn. It has been customary in the past to produce mushroom in plastic bags. This is accomplished by pasteurising a substrate, inoculating the substrate with mushroom spawn seeds, transferring the mixture into plastic bags and after a suitable method of incubation, collecting the mushrooms at maturity. The inoculation is performed by mixing the substrate and the fungus seeds in the open air. This operation also requires for the pasteurisation room to remain open for several hours. Moreover, since it is highly desirable to prevent contamination of the mushroom from contact with microbes in the air, the transfer of inoculated, pasteurised substrate from one container to plastic bags involves some difficulty. US Patent No. 2851821 discloses mushroom spawn grown in a plastic bag. The bag is closed by turning the ends of the bag and forming a chimney, and it is sealed by placing a wad of cotton or the like in the chimney thus formed. In another embodiment, a tube is inserted in the top of the bag and the bag gathered around the tube of the string, A filter plug is then placed in the tube. Another method is described in US Patent No. 4027427 wherein the spawn is grown in a plastic bag provided with a temporary filter cover. This bag is provided with a removal closure mechanism for filling the bag and maintaining sterility during the processing steps. US Patent No. 4977702 discloses a bag for the production of eatable mushrooms which is provided with a number of gas exchange surfaces or membranes which are impervious to outside micro organisms, thereby avoiding contamination of the nutrient substrate by outside micro organisms. Inoculation can be performed by injection of the inoculum in suspension trough the plastic bag. The gas exchange membranes of the bag may be made of Dupont Tyvek ® spun bonded polyolefin. US Patent No. 4311477 teaches a bag for cultivating mushrooms constructed, at least in part, from a micro-porous film having gas permeability, but which does not pass bacteria and infectious microbes. Although it has been found that the above-listed bags are suitable for the production of mushroom spawn, it has also been found that the growth of the spawn is hindered within the bags by the lack of adequate airflow and direction of the airflow at an appropriate volume to the substrate within the bags. Accordingly, it is an object of the present invention to provide an improved plastic bag for the growth of mushroom spawn which is low in cost, easy to produce and which circulates uncontaminated air to the substrate within the bag in an improved manner, thereby resulting in improved mushroom production rates and quantities. The following US and foreign references were identified as being relevant to the present invention: US Patent Nos. 4878312 CHIMICU, 4977702 FORTIN ET AL: EP No. 83-742416; JAPAN 2286-012; JAPAN 2-4673; GERMANY 3734509-A; SWITZERLAND 647-209-A; GREAT BRITAIN 1176188 and GERMANY 148-436. According to the present invention there is provided a bag for cultivation of mushroom spawn, said bag comprising a front wall having a plurality of openings disposed therethrough, a back wall, a top and a bottom and left and right sides and a plurality of gas permeable sealing strips sealed to said front wall and covering each of said openings, characterised in that said openings are arrayed in a pair of parallel rows proximate respectively said top and bottom of said bag, and that said sealing strips cover said rows, each sealing strip having a length sufficient to cover all of the openings in the row that it covers and a width less than the distance between said top and bottom of said bag, said openings and said sealing strips being constructed and arranged so as to reduce dry spots in said mushroom spawn and improve spawn yield. In a preferred embodiment, the openings through the bag walls are of substantially equal size, in a lateral array trough the front wall of the bag, and spaced inwardly from the left and right sides. The openings are preferably oval in shape which facilitates cutting of the openings from the plastic used to manufacture the bag and also facilitates removal of the plastic from the oval openings after cutting. The openings are preferably 1.25 cm (½") wide by 3.75 cm (1½") long and the sealing strips are approximately 2.5cm (1") to 3.75 cm (1½") wide and at least 5 cm (2") long to insure complete sealing of the opening by the sealing strip, although again other sizes may be used. In a preferred embodiment, the sealing strip comprises spun bonded microporous polyolefin; i.e. DuPont Tyvek® type material. The sealing strips are sealed to the bag wall, preferably, in a rectangular sealing grid which extends entirely around the opening of the bag wall. The aforesaid openings are preferably arrayed through the front wall of the bag in an upper row having a centreline approximately 16.5 cm (6 ½") from the top of the bag and the gas permeable film strip is spaced approximately 14 cm (5½"), (centreline), from the top of the bag. The lower row of openings is preferably spaced with a centreline approximately 12.5 cm (5") plus or minus 1.25 cm (a half inch) from the bottom of the bag and one of the gas permeable film strips is spaced approximately 11.4 cm (4½") (centreline) plus or minus 1.25 cm (a half inch) from the bottom of the bag. The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of a prior art bag. Figure 2 is a front perspective view of an additional prior art bag for the growth of mushroom spawn. Figure 3 is a front perspective view of one embodiment of an improved mushroom spawn bag according to the present invention. Figure 4 is a cross sectional view taken along line 4-4 in Figure 3. Figure 5 of the drawings is an enlarged view, partially broken away for purposes of illustration, of the improved mushroom spawn bag shown along line 5-5 in Figure 3. While the present invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the invention is not limited thereto except insofar as those who have the disclosure before them are able to make modifications and variations without departing from the scope of the invention. As shown in Figures 1 and 2, it is known to use a polyethylene plastic bag 10 or 11 for the growth of mushroom spawn 12. Mushroom spawn 12 in turn is injected into nutrient substrate 14 contained within bag 10 for the growth of mushrooms 12. Plastic bag 10 is characterised by its opacity and its water resistance, and is provided with perforations 16 which in the case of U.S. Patent No. 4977702 are .3 cm in diameter and .10 cm apart. These perforations 16 are covered by a gas exchange membrane 18 which is hermetically sealed around and covers each individual perforation 16. Gas exchange membrane 18 is permeable to air and impermeable to particles, like dust, powder and micro organisms. For example, bag 10 or 11 can be made of polyethylene which is sold by First Brands Industries Corporation under the trade mark Glad® Bags. The gas exchange membranes 18 for example, are made of porous material which is sold by DuPont Company, Wilmington, Delaware, U.S.A. under the name Tyvek®. More specifically, the Tyvek used is the type 10, style 1059b characterised by its opacity of 85 Eddy, its porosity of 11 to 31 seconds/100 cc/2.54 square cms. (11 to 31 seconds/100 cc/square inch), its water resistance through the hydrostatic pressure test of 120 to 185 cms (47 to 73 inches) and having no anti-static agents or aerosol sprays. The nutrient substrate 14 is packaged into the plastic bag 10 to form mushroom molds of 10 to 30 kilograms. The substrate 14, (preferably straw) is preferably cut into pieces of 5 cm, soaked for 12 hours and finally drained. In use the substrate 14 is first pasteurised, then, secondly, cooled during the night. The substrate 14 has its temperatures raised to between 21°C (70°F) and 27°C (80°F) trough water vapour. Again, the substrate is allowed to cool down during the following night. The most important aspect of the preferred thermal treatment resides in a two temperature peaks imposed on the substrate in two different phases. The third step of the prior art method of growing mushroom spawns 12, comprises inoculating the pasteurised nutrient substrate 14 with a suspension of the desired mushrooms produced in liquid fermentation. The inoculum is prepared for example, using a fermenting device of type Vertus ® or type Belco® with a liquid medium. Under required conditions of constant agitation and separation of the liquid medium, the inoculum is recovered after 4 days of incubation at 25° C. Preferably, the conditions of incubation are characterised by a constant agitation of the substrate and a renewed air supply. An inoculum density of approximately 8 grams of dry weight mycelium per litre of medium is obtained through the use of this method. Because the inoculum is in suspension, it renders the inoculation of the pasteurised substrate through the walls of the plastic bag possible. The inoculation is preferably made at the rate of 1 litre of inoculum per 20 kilograms of substrate, five millilitres per shot. The fourth step of the process comprises incubating the inoculated pasteurised nutrient medium. Once the inoculation is complete, the plastic bags are placed vertically in an incubation room. The most desired incubation conditions will be a temperature of 24° C, a humidity factor of 90%, total darkness and no renewed air supply. The spawn running requires 15 to 21 days. Thereafter, the gas exchange surface membranes 18 are removed and the temperature is raised 2° C permitting the development of the fruit bodies from the appeared primordia through the perforations. A great number of fruit bodies having the normal shape and colour inherent in pleurotus or volvaria are formed. The sixth and last step of prior art mushroom spawn growth comprises collecting the edible mushrooms at maturity from the first flush and then every 7 to 10 days for several weeks. As shown in Figure 3 of the drawings, in the present invention, an improved bag 20 for the cultivation of mushroom spawn 12 is disclosed. Bag 20 has a front wall 22, a back wall 24 and a plurality of openings 26 disposed through the front wall 22. Bag 20 further has a top 28, a closed bottom 30, a sealed left side 32 and a sealed right side 34. One of the principal improvements of the present invention over the prior art is the use of a pair of gas permeable sealing strips 36 and 38 sealed to the outside surface 40 of the front wall 22 over openings 26. Preferably, the openings 26 will comprise a pair of parallel rows 42 and 44, respectively, near the top 28 and the bottom 30 of bag 20. In the preferred embodiment shown, a pair of openings 26a and 26b are located proximate the top 28 of bag 20. An additional pair of openings 26c and 26d are located proximate bottom 30 of bag 20. This arrangement provides more uniform breathability of the mushroom spawn 12 through the gas permeable sealing strips 36 and 38. In addition, it reduces loss of moisture from within bag 20, thereby reducing dry spots in the mushroom spawn 12, and thus, improving spawn yields. As further seen in Figure 3, the pairs of openings 26a, 26b, 26c and 26d are of substantial equal size and are laterally arrayed through the front wall 22 of the bag 20 inwardly of the left side 32 and right side 34 respectively of bag 20. Row 42 is the upper row and row 44 is the lower row. Openings 26, in the embodiment shown, are substantially oval in shape in order to facilitate cutting of bag 20 during manufacture, and to facilitate removal of the resulting oval cut out from the openings 26. In the preferred embodiment, openings 26 are approximately 1.25 cm (½") wide by 3.75 cm (1½") long so as to ensure adequate air flow through the openings 26, but prevent excessive loss of moisture from the bag. Sealing strips 36 and 38 are approximately 2.5 cm (1") to 3.75 cm (1½") wide and at last 5 cm (2") long so as to ensure complete sealing of openings 26a, 26b, 26c and 26d of the sealing strips. In the preferred embodiment, sealing strips 36 and 38 each comprise a continuous strip of gas permeable film sealed horizontally above and below openings 26 from the left side 32 to the right side 34 of the bag 20 and sealed vertically on the left side 46 and the right side 48 of each of said openings 26. In the embodiment shown, these seals comprise left side seals 46a, 46b, 46c and 46d and right side seals 48a, 48b, 48c and 48d, top seals 36a and 38a and bottom seals 36b and 38b. The sealing of continuous strips 36 and 38 covers the openings 26 and thereby substantially restricts passage of moisture therethrough while allowing the flow of air. In the preferred embodiment, the sealing strips 36 and 38 are constructed of spun bonded micro porous polyolefin; i.e. Tyvek ®. Tyvek type 10 style is preferred. One type of Tyvek type 10 is 1059b, is previously known in the prior art as described above. Two other types that may be used are style 1056d and 1073b. Additionally, the water vapour transmission rate of the three types of type 10 Tyvek are 694 grams/m 2 /24 hours for type 1056d; 684 g/m 2 /24 hours for type 1059b and 614 g/m 2 /24 hours for type 1073d. Type 1073b has a water vapour transmission rate of 641 grams per /m 2 /24 hours. It has been found that these styles of Tyvek type 10 are suitable for use in the manufacture of gas permeable sealing strips 36 and that in use they substantially restrict passage of moisture through openings 26 but allow ready passage of air. In the preferred embodiment, the upper row 42 of openings 26 have centrelines 26e and 26f, spaced approximately 15.25 cm (6") plus or minus 1.25 cm (½") from the top 28 of bag 20. Gas permeable sealing strip 36 has a top edge 36a spaced approximately 14 cm (5½") from the top 28 of bag 20. The lower row 44 of openings 26 are spaced approximately 12.5 cm (5") plus or minus 1.25 cm (½") from the bottom 30 of bag 20 to their centrelines 26f and 26h and gas permeable strip 38 is spaced approximately 11.4cm (4½") plus of minus 1.25 cm (½") from the bottom 30 of bag 20 to its centreline 38c. In the preferred embodiment, bag 20 is constructed of polyethylene having a thickness of 2 mils to 10 mils. Sealing strips 36 and 38 preferably have a thickness of 5 mils to 10 mils and a porosity of 4 cubic metres per minute (138 cubic feet per minute) according to the Frazer test, ASTM D737. It has been found through the use of bags such as bag 20, that the quantity of mushroom grown using identical spawning techniques is increased from 15% to 33% without an increase in cost. Accordingly, a strong demand for this product is anticipated.

Claims: A bag for cultivation of mushroom spawn, said bag comprising a front wall (22) having a plurality of openings (26) disposed therethrough, a back wall (24), a top (28) and a bottom (30) and left and right sides (32,34) and a plurality of gas permeable sealing strips (36,38) sealed to said front wall (22) and covering each of said openings, characterised in that said openings (26) are arrayed in a pair of parallel rows (42,44) proximate respectively said top (28) and bottom (30) of said bag (20), and that said sealing strips cover said rows (42,44), each sealing strip (36,38) having a length sufficient to cover all of the openings (26) in the row (42 or 44) that it covers and a width less than the distance between said top (28) and bottom (30) of said bag (20), said openings (26) and said sealing strips (36,38) being constructed and arranged so as to reduce dry spots in said mushroom spawn and improve spawn yield. A bag according to claim 1, wherein said openings (26) are of substantially equal size, laterally arrayed trough said front wall (22) of said bag (20) inwardly of said left and right sides (32,34), said openings (26) further comprising an upper row (42) and a lower row (44) spaced apart from said upper row (42), said upper row (42) being parallel to said top (28) of said bag and said lower row (44) being parallel to said bottom (30) of said bag whereby air is permitted to circulate more freely trough said bag. A bag according to claim 2, wherein said upper row (42) of openings (26) is spaced approximately 15 cms (six inches) from said top (28) of said bag and one of said strips (36,38) has a top edge spaced approximately 14 cms (five and one half inches) from said top (28) of said bag. A bag according to claim 2 or 3, wherein said lower row (44) of openings (26) is spaced approximately 12.5 cms (five inches) from said bottom (30) of said bag and one of said strips (36, 38) is spaced approximately 11.4 cms (four and one half inches) from said bottom (30) of said bag. A bag according to any preceding claim, wherein each of said openings (26) is substantially oval in shape so as to facilitate manufacture. A bag according to any preceding claim, wherein each of said openings (26) is approximately 1.25 cm (½") wide by 3.75 cm (1½") long so as to ensure adequate air flow trough said openings (26). A bag according to any preceding claim, wherein the or each strip (36,38) is approximately 2.5 cm to 3.75 cm (1½") wide and at last approximately 5 cm (2") long so as to ensure complete sealing of said openings by said strip or strips (36,38). A bag according to any preceding claim, wherein said bag (20) comprises polyethylene having a thickness of 2 mils to 10 mils. A bag according to any preceding claim, wherein the or each strip (36,38) has a thickness of five to ten mils and is constructed of spunbonded microporous polyolefin. A bag according to any preceding claim, wherein said strip or each of said strips (36,38) has a water vapour transmission rate of 600-700 grams/m 2 /24 hours.

Inventors: SIEBERT LESTER, SPREHE GREGORY S, TOWNE WILLIAM, SIEBERT, LESTER, SPREHE, GREGORY S., TOWNE, WILLIAM
Applicants: COMPAC INT INC, COMPAC INTERNATIONAL, INC.
Application year: 1994
Main classification: A01G1
IPC codes: A01G1, B31B19, B31B39